Collagen is a major protein component forming connective tissues of animals. Collagen has conventionally been used in various cosmetics with an objective of providing the skin with tension and elasticity. More recently, collagen is attracting attention as a material for foods and the like due to the discovery of various physiological effects such as promotion of bone calcium absorption, activation of neurotransmission, and the like.
Various drinks into which collagen or collagen substance, such as gelatin (a collagen hydrolysate) or collagen peptide obtained by further hydrolyzing gelatin, is incorporated with an objective of reinforcing collagen are commercially available.
Fermented milk drinks obtained by acidifying milk by fermenting with lactic acid bacteria, Bifidobacterium group bacteria, yeasts, and the like and acidic milk drinks obtained by directly acidifying milk with an acidifier are excellent drink shaving a flavor characteristic to milk. However, if these drinks are stored for a long period of time, casein proteins in milk components are condensed and precipitated, impairing both the appearance and flavor. Milk proteins are stabilized by the addition of a stabilizer such as pectin, carboxymethylcellulose, propylene glycol arginate, water-soluble soybean polysaccharide, and the like. Many acidic milk drinks containing these stabilizers are commercially available.
However, if a collagen substance is added to fermented drinks or acidic milk drinks (hereinafter collectively referred to as “acidic milk drinks”), stabilization by the addition of the stabilizer is impaired. As a result, long-term storage stability becomes insufficient.
Although such a decrease in stability can be improved to a certain extent by adding a large amount of stabilizer, the addition of a large amount of stabilizer makes an unfavorable taste of the stabilizer predominant. Beverages easy to drink and having a good flavor cannot be obtained. In addition, the drinks become viscous and difficult to swallow. The long-term storage stability can be improved also by decreasing the amount of collagen substance added to the acidic milk drinks. The amount of collagen substance that improves the storage stability, however, is too small for the acidic milk drinks to exhibit the anticipated effect of the addition of collagen substance.
In this manner, it is difficult for acidic milk drinks containing various stabilizers to maintain their stability if collagen substance are added. Development of an acidic milk drink reinforced with collagen substance without impairing stability of milk proteins due to stabilizers has been desired.